JP2759720B2 - Manufacturing method of super absorbent paper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing paper having good water absorption, and an object of the present invention is to use it for information paper using an aqueous ink such as an ink jet and to prevent ink from bleeding.

[0002]

2. Description of the Related Art Ink jet systems are widely used as printers used in computers and word processors. Since this ink contains water, it has a drawback that it oozes along the pulp fiber in the paper, or its absorption into the paper is delayed, and the ink adheres to other parts to stain the characters.

In order to solve this problem, a method of mixing a highly water-absorbing resin such as a crosslinked product of sodium polyacrylate into paper has been studied. In addition to absorbing water, it swells to cause poor drying, and calcium ions and aluminum ions in the paper stock reduce the water absorbing ability, so that the initial purpose cannot be achieved.

Japanese Patent Application Laid-Open No. 58-214597 discloses a method of making paper by adding a water-insoluble polymer to a stock, but the purpose of the method is to enhance paper strength and to absorb water. No improvement in performance is expected.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to prevent bleeding of an aqueous ink and easily obtain a paper having a high water absorbing ability suitable for printing a clear image.

[0006]

In order to achieve the above object, the present invention is configured as follows. That is, the present invention relates to N-
It is characterized in that a paper stock mixed with thermosensitive water-absorbing resin fine particles composed of a crosslinked product of isopropylacrylamide polymer is heated to a temperature higher than the phase transition temperature of the thermosensitive resin, and papermaking is performed in a state where the water absorbing ability is lost. Further, in the present invention, the particle size of the superabsorbent resin particles is 30 μm or less in a dry state, and the mixing ratio into the stock is 0.5 to 5.
0% by weight.

[0007]

The crosslinked N-isopropylacrylamide polymer has a temperature sensitivity, and if it is below the phase transition temperature, it becomes a gel that has absorbed water in water, and loses water absorption in water above the phase transition temperature. A general papermaking method is to filter a paper stock in which pulp or the like is suspended in water, form a wet web by filtering through a wire, and press and dry the paper.
-When the crosslinked isopropylacrylamide polymer fine particles are mixed, if the temperature of the stock is equal to or higher than the phase transition temperature, the resin has lost its water absorbing ability, and is easily dispersed in an aqueous liquid;
There is no trouble in each process from papermaking to drying. When using paper, it is customary to use the paper at room temperature. Since the temperature is lower than the phase transition temperature, the resin has recovered its water absorbing ability and can prevent bleeding of the aqueous ink.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, in the present invention, papermaking is carried out by using fine particles of a crosslinked N-isopropylacrylamide polymer at a high temperature which is higher than the phase transition temperature of the resin, and in which the resin fine particles have lost their water absorbing ability. It is characterized by doing. Papermaking temperature is 3
In the range of 0 ° C. or more and 50 ° C. or less, it can be appropriately selected according to the phase transition temperature of the resin. N-isopropylacrylamide can be copolymerized with various water-soluble monomers, and when the copolymerization ratio of the hydrophilic monomer is high, the phase transition temperature increases. Examples of water-soluble monomers copolymerizable with N-isopropylacrylamide include nonionic monomers such as (meth) acrylamide, acrylonitrile, and vinyl acetate; and anions such as (meth) acrylic acid, acrylamidomethylpropylsulfonic acid, fumaric acid, and itaconic acid. And cationic monomers such as a dialkylaminoalkyl (meth) acrylate or a quaternary compound thereof, and a dialkylaminoalkyl (meth) acrylamide or a quaternary compound thereof.

In particular, the cationic monomer copolymer has a positive charge and is easily adsorbed on the pulp surface, which is advantageous for improving the yield of the water-absorbing resin fine particles. These monomers can be copolymerized with N-isopropylacrylamide in combination of plural kinds. The particle size of the water-absorbing resin fine particles is 30 μm or less in a dry state, and particularly preferably 15 μm or less. If the particle size is too large, the irregularities on the paper surface are large, and the printability decreases. In order to produce such fine particles, it is easy to finely pulverize the polymer, and it is also easy to obtain fine particles during polymerization by emulsion polymerization or the like. In the present invention, the amount of the water-absorbing resin fine particles mixed into the stock is 0.1 to pulp.
The range of 5 to 5% by weight is preferable. If it is too small, it is ineffective, and if it is too large, the cost becomes high. Hereinafter, the present invention will be described in detail with reference to Examples.

Example 1 A mixture of 70 g of N-isopropylacrylamide, 5 g of acryloyloxyethyltrimethylammonium chloride and 25 g of deionized water was mixed with 2 g of a 1% aqueous solution of methylenebisacrylamide and 2,2'-azobis (2-amidinopropane) hydrochloride. 1 g of a 1% salt aqueous solution was added and mixed, and polymerization was carried out in a Teflon container to obtain a bulk polymer. The water absorption ratio of this resin was 85 times, and the phase transition temperature was 36 ° C. This resin is finely pulverized, and the fine powder that has passed through a sieve having an opening of 0.015 mm is referred to as resin-1. LBKP 70%, NBK
A pulp having a mixing ratio of P30% is beaten to 400 ml of Canadian standard freeness, and resin-1 is mixed with talc 8% and emulsion size 0.4%, and a liquid band 3% is added to adjust the pH to 5.5. After the adjustment, papermaking was performed at a temperature of 45 ° C. The amount of each chemical added is the weight ratio to pulp. The wet paper was calendered at a linear pressure of 500 kg / cm to smooth the paper surface, and then dried and subjected to a test.

[0011]

According to the present invention, various test papers are fed at room temperature of 25 ° C. using an ink jet printer HG-4000PC manufactured by Seiko Epson Corporation, and after printing one page of B-5 size paper, the copy paper is immediately pressed on the surface. The presence or absence of transfer and the bleeding of printing were observed. The paper made under the conditions of Example 1 showed no transfer to copy paper and no ink bleeding at a mixing ratio of Resin-1 of 1% and 2%. On the other hand, in the case of the resin-free paper, the characters were transferred to the copy paper, and the printing was blurred. Further, the resin-mixed paper made at 30 ° C. was not suitable for printing due to the formation of fine holes on the paper surface. The method for producing the resin-mixed paper of the present invention is easy, has an excellent ink absorption effect, suppresses a phenomenon called show-through, and has clear printing.

Claims (3)

(57) [Claims] 1. A paper stock mixed with thermosensitive water-absorbing resin fine particles composed of a crosslinked N-isopropylacrylamide polymer is heated to a temperature higher than the phase transition temperature of the thermosensitive resin, and papermaking is performed in a state where the water absorbing ability is lost. A method for producing highly water-absorbing paper, characterized in that: 2. The particle size of the water-absorbing resin fine particles in a dry state is 30 μm.
2. The method for producing superabsorbent paper according to claim 1, wherein m is equal to or less than m. 3. The process for producing superabsorbent paper according to claim 1, wherein the mixing ratio of the water-absorbent resin fine particles is 0.5 to 5.0% by weight based on the pulp in a dry state.